Integrated blood handling system having active gas removal system and method of use

ABSTRACT

Apparatus and methods for pumping and oxygenating blood are provided that include a gas removal system. An integrated blood processing unit is provided in which a gas removal/blood filter, pump and blood oxygenation element are mounted within a common housing. The gas removal system includes a sensor mounted on the housing to sense the presence of gas, and a valve is operably coupled to the sensor to evacuate gas from the system when the sensor detects an accumulation of gas.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/780,923, filed Feb. 9, 2001.

FIELD OF THE INVENTION

The present invention relates to apparatus and methods for pumping,oxygenating and filtering blood having means for removing air or othergasses from the blood.

BACKGROUND OF THE INVENTION

Each year hundreds of thousands of people are afflicted with vasculardiseases, such as arteriosclerosis, that result in cardiac ischemia. Formore than thirty years, such disease, especially of the coronaryarteries, has been treated using open surgical procedures, such ascoronary artery bypass grafting. During such bypass grafting procedures,a sternotomy is performed to gain access to the pericardial sac, thepatient is put on cardiopulmonary bypass, and the heart is stopped usinga cardioplegia solution.

The development of minimally invasive techniques for cardiac bypassgrafting, for example, by Heartport, Inc., Redwood City, Calif. andCardioThoracic Systems, Inc., Menlo Park, Calif. have placed a premiumon reducing the size of equipment employed in the sterile field. Whereasopen surgical techniques typically provide a relatively large surgicalsite that the surgeon views directly, minimally invasive techniquesrequire the placement of endoscopes, video monitors, and variouspositioning systems for the instruments. These devices crowd the sterilefield and can limit the surgeon's ability to maneuver.

At the same time, however, the need to reduce priming volume of theoxygenator and pump, and the desire to reduce blood contact withnon-native surfaces has increased interest in locating the oxygenatorand pump as near as possible to the patient.

In recognition of the foregoing issues, some previously knowncardiopulmonary systems have attempted to miniaturize and integratecertain components of cardiopulmonary systems. U.S. Pat. Nos. 5,266,265and 5,270,005, both to Raible, describe an extracorporeal bloodoxygenation system having an integrated blood reservoir, an oxygenatorformed from a static array of hollow fibers, a heat exchanger, a pumpand a pump motor that is controlled by cable connected to a controlconsole.

One drawback of systems of the type described in foregoing patents,however, arises during priming of the extracorporeal circuit, and inparticular, in the need to use large quantities of saline or donor bloodto prime the systems. Such fluids are required to flush air out of thesystem and, because they are relatively incompressible, ensure that thepump used in the extracorporeal circuit develops sufficient pressurehead to propel oxygenated blood back to the patient.

In view of this limitation of previously known blood handling systems,it would be desirable to provide a blood handling system and methodsthat automatically remove air from an extracorporeal blood circuit.

It further would be desirable to blood handling systems and methods thatpermit one or more additional blood processing components, such as aheat exchanger, to be added to an extracorporeal blood circuit withouthaving to prime the component prior to bringing that component online,thereby reducing disruption to operation of the blood handling system.

It also would be desirable to provide an extracorporeal blood handlingsystem and methods wherein the blood handling system has compact sizeand low surface area, and reduces contact between the blood and foreignsurfaces, thus reducing priming volume, hemolysis and plateletactivation.

It still further would be desirable to provide a blood handling systemand methods that provide progressive filtration of blood passing throughthe system, thus reducing the risk that a single blood filter elementwill become clogged during extended operation.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide apparatus and methods for handling blood that automaticallyremove air from an extracorporeal blood circuit.

It is another object of the present invention to provide a bloodhandling system and methods that permit one or more blood processingcomponents, such as a heat exchanger, to be added to an extracorporealblood circuit without having to prime the component prior to bringingthat component online, thereby reducing disruption to operation of theblood handling system.

It is yet another object of this invention to provide an extracorporealblood handling system and methods wherein the blood handling system hascompact size and low surface area, and reduces contact between the bloodand foreign surfaces, thus reducing priming volume, hemolysis andplatelet activation.

It is a further object of the present invention to provide a bloodhandling system and methods that provide progressive filtration of bloodpassing through the system, thus reducing the risk that a single bloodfilter element will become clogged during extended operation.

These and other objects of the present invention are accomplished byproviding a blood handling system comprising an integrated bloodoxygenator and pump system having means for removing air or other gasesfrom the extracorporeal blood circuit. In accordance with the principlesof the present invention, the blood handling system includes a gascollection plenum, a line adapted to be connected to a suction source,and a sensor that controls coupling of the suction source to the gascollection plenum to selectively remove gas from the blood handlingsystem. The blood handling system of the present invention therefore maybe initially primed with little or no saline or donor blood, and withreduced risk of hemodilution.

Moreover, additional components may be added to an existingextracorporeal circuit with little or no additional priming, and any airor other gases introduced into the system will be evacuated with nosubstantial impact on operation of the blood pump of the blood handlingsystem.

In a preferred embodiment, a blood handling system of the presentinvention maintains total or partial bypass support for a patient andcomprises a housing having a blood inlet, a blood outlet, a gascollection plenum, a blood oxygenation element, a blood pump and a gasremoval system.

Blood entering the housing via the blood inlet flows through the gascollection plenum and a first blood filter component that forms part ofthe gas removal system. Air or other gases entrained in the blood areseparated from the blood and collect in the gas collection plenum. Asensor disposed in communication with the gas collection plenum senses aparameter indicative of a level or volume of gas collected in theplenum, and selectively evacuates the plenum by coupling the plenum to asuction source, such as a standard operating room suction port.

Blood exiting the first blood filter component passes to a centrifugalblood pump, which propels the blood through the blood oxygenationelement. The blood oxygenation element preferably comprises an annularfiber bundle, e.g., an annular bundle of hollow gas exchange tubes,positioned within the housing. In accordance with another aspect of thepresent invention, the annular filter bundle serves as a second bloodfiltration element.

Blood exiting the blood oxygenation element then passes through anadditional blood filter element before exiting from the housing throughthe blood outlet. Blood processed through the system therefore passesthrough multiple blood filters, which may be progressively finer,distributed throughout the housing, thereby reducing the risk that anyone of the filters will be overburdened and clog during extended use ofthe system.

In still another aspect of the invention, the blood oxygenation elementreceives blood from the blood pump on a side of the annular fiber bundlethat is diametrically opposite to the blood outlet. The inlet to theannular fiber bundle preferably includes an inlet manifold and the bloodoutlet of the housing preferably has an outlet manifold. The inlet andoutlet manifolds preferably extend longitudinally along diametricallyopposite sides of the blood oxygenation element, so that blood flowsfrom one side to the diametrically opposite side of the bloodoxygenation element.

In a preferred embodiment, the gas removal system includes a gasremoval/blood filter element having a cylindrical shape. The gasremoval/blood filter comprises a support structure that supports ascreen-like material having an effective pore size between 40 and 250microns. Alternatively, the gas removal/blood filter element maycomprise a pleated filter material. Blood is introduced into the gascollection plenum via the blood inlet in a direction substantiallytangential to the gas removal/blood filter, to increase residence timeof the blood within the gas collection plenum, thereby enhancingseparation of entrained gas.

In still another aspect of the present invention, the housing of bloodoxygenation element includes at least one relief area positionedradially inward from the annular fiber bundle. More preferably, a reliefarea is positioned radially inward from each of the inlet and outletmanifolds to permit expansion of the annular fiber bundle at theselocations, and to increase the porosity of the fibers in the manifoldarea and decrease resistance to flow.

Methods of operating the blood handling system of the present inventionalso are provided.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects and advantages of the present invention willbe apparent upon consideration of the following detailed description,taken in conjunction with the accompanying drawings, in which likereference characters refer to like parts throughout, and in which:

FIG. 1 is a schematic depiction of an extracorporeal blood circuit usingthe blood handling system of the present invention;

FIGS. 2A and 2B are, respectively, perspective and exploded perspectiveviews of the integrated blood-processing component of the presentinvention;

FIG. 3 is a side-sectional view of the integrated blood processingcomponent of the present invention;

FIG. 4 is a cross-sectional view of apparatus similar to that of FIG. 3,taken along line 4-4 in FIG. 3, depicting the use of relief areasadjacent to the inlet and outlet manifolds;

FIGS. 5A and 5B are, respectively, perspective and cross-sectional viewsof a gas removal/blood filter element of the gas removal system of thepresent invention;

FIGS. 6A and 6B are, respectively, perspective and cross-sectional viewsof an alternative gas removal/blood filter element of the gas removalsystem of the present invention;

FIG. 7 is a cross-sectional view of a gas removal/blood filter of thegas removal system of the present invention configured for use inpreviously known extracorporeal blood processing systems;

FIG. 8 is a side-sectional view of alternative embodiment of theintegrated blood processing component of the present invention;

FIGS. 9A and 9B are, respectively, exploded perspective and side viewsof the impeller, bearing assembly and shaft of the blood pump of thepresent invention;

FIG. 10 is an exploded perspective view depicting an injection moldingprocess for the impeller of FIGS. 9;

FIGS. 11A and 11B are front and rear perspective views of the bloodhandling system of the present invention; and

FIGS. 12A and 12B are representative screens depicting the display ofparameters monitored and/or controlled by the blood processing system ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, extracorporeal blood circuit 10 including bloodhandling system 30 of the present invention is described. Extracorporealblood circuit 10 is designed for maintaining a patient on full orpartial bypass support, for example, during a coronary artery bypassgraft procedure or mitral valve repair procedure.

Extracorporeal blood circuit 10 includes venous line 11 that carriesdeoxygenated blood from patient P to blood handling system 30, andarterial line 12 that returns oxygenated blood to the patient. Each ofvenous line 11 and arterial line 12 are coupled to the patient through asuitable cannula, which is per se known. In accordance with knownmethods, the venous and arterial cannulae may be positioned in anysuitable vein or artery.

Venous line 11 is coupled to inlet line 13 of blood handling system 30via lines 14, 15 and 16. Line 14 preferably includes dynamic reservoir17 that can be selectively added and removed from the circuit usingvalves 18 and 19. Dynamic reservoir 17, which preferably is a flexiblestorage bag, permits blood to be stored or supplied to blood handlingsystem 30 as necessary. Valves 18 and 19 control blood flow into and outof dynamic reservoir 17. One advantage of this arrangement ofextracorporeal blood circuit 10 is that the pump of the blood processingcomponent may be used to fill and evacuate the dynamic reservoir 17during operation by simply manipulating valves 18 and 19. Alternatively,a conventional venous storage reservoir may be used instead of dynamicreservoir 17.

Line 15 includes valve 20 which may be activated to direct blood comingfrom the patient to either or both of lines 13 and 16. Line 16, whichmay include additional valving (not shown) permits additional bloodprocessing unit 21, such as an additional filter or heat exchanger, tobe included in extracorporeal blood circuit 10. Optional recirculationline 22 includes valve 23, and permits a portion of the output of bloodhandling system 30 to be recirculated to the input of the blood handlingsystem, or used in administration of cardioplegia to the patient.

Blood handling system 30 includes integrated blood processing component31 coupled to drive unit 32 and controller 33. In accordance with oneaspect of the present invention, blood handling system 30 has a gasremoval system including sensor 37 and valve 36 adapted to be coupled tosuction source 34 via line 35. Valve 36 and sensor 37 preferably areelectrically coupled to controller 33 so that controller 33 can regulateoperation of valve 36 responsive to an output of sensor 37. As explainedin greater detail hereinafter, the gas removal system of the presentinvention removes air and other gases from extracorporeal blood circuit10 and blood processing component 21 during priming and operation of thebypass system.

Referring now to FIGS. 2A, 2B and 3, integrated blood precessingcomponent 31 combines the features of previously known bloodoxygenators, blood pumps, and blood filters into a single housing. Inaccordance with one aspect of the present invention, the blood handlingsystem also provides for continuous monitoring and removal of air orother gases from the extracorporeal blood circuit during priming andoperation.

Blood processing component 31 includes housing 40 having blood inlet 41,blood outlet 42, recirculation outlet 43, gas inlet port 44, gas outletport 45 and gas removal port 46. Blood outlet 42 and recirculationoutlet 43 are disposed from blood outlet manifold 47, which is disposeddiametrically opposite blood inlet manifold 48 of housing 40. Bloodprocessing component 31 preferably includes tabs 49 or other means forcoupling blood processing component 31 to reusable drive unit 32.

Illustratively, housing 40 comprises a series of parts that each definea compartment: gas collection plenum 50, central void 51, upper gasplenum 52, annular fiber bundle compartment 53, lower gas plenum 54 andpump space 55. In a preferred embodiment, central void includes a largerdiameter upper portion and a smaller diameter lower portion. As will ofcourse be understand, the parts shown in exploded view in FIG. 2B couldbe molded or cast in more or fewer pieces.

Gas collection plenum 50 encloses a gas removal/blood filter 56 thatextends within upper portion of central void 51. Gas removal/bloodfilter 56 causes gas entrained in blood introduced into the gascollection plenum to separate and collect in the upper portions of gascollection plenum 50. Gas removal/blood filter 56 comprises generallyconical upper wall 57, baffled support structure 58 and filter material59. Blood inlet 41 is displaced tangentially relative to the centerlineof housing 40, so that blood passing through blood inlet 41 into gascollection plenum 50 swirls around upper wall 57, which is preferablyfluid impermeable.

Upper wall 57 also preferably includes a chamber having a centralopening through its upper surface, which communicates with the upperportion of gas collection plenum 50. This configuration allows any gasthat passes through filter material 59 to escape through the opening inupper wall 57 and be evacuated from gas collection plenum 50.Advantageously, this feature facilitates rapid and easy priming of bloodprocessing component 31, as described hereinbelow.

Filter material 59 comprises one or multiple layers of a screen-likematerial having an effective pore size of between 40 and 250 microns,and is mounted to baffled support structure 58. Filter material 59serves to exclude bubbles from the blood flow by maintaining theswirling action of the blood in the central void for a sufficient timeto allow the bubbles to rise to the gas collection plenum. Because theblood circulates around the outside of gas removal/blood filter 56 incentral void 51, bubbles impinge against filter material 59tangentially, and thus “bounce off.” Filter material 59 preferably alsoforms a first stage of a progressive blood filter that is distributedthroughout the blood processing component, and filters out relativelylarge particulate matter.

As illustrated in FIGS. 5A and 5B, support structure 58 forms an opencage 60 having longitudinal struts 61 and support rings 62. Struts 61extend radially inward and preferably include radiused inner ends 63.Struts 61 serve as baffles to reduce swirling of blood that has passedthrough filter material 59. In an alternative embodiment, shown in FIGS.6A and 6B, struts 61 are further extended radially inward to form fluidimpermeable cruciform structure 63.

Referring again to FIG. 3, blood oxygenation element 70 is disposedwithin annular fiber bundle compartment 53, and comprises a multiplicityof gas permeable fibers arranged in an annular bundle. As is well knownin the art, the gas permeable fibers are potted near the upper and lowerends of the bundle so gas may pass through the interior of the fibersvia the ends of the fibers, while allowing blood to pass along theexteriors of the multiplicity of tubes in the bundle. The bundletherefore includes upper potting region 71 that separates the blood flowregion within the annular bundle from upper gas plenum 52, and lowerpotting region 72 that separates blood flow region from the lower gasplenum 54.

Blood passing into the annular fiber bundle compartment 53 from bloodinlet manifold 48 therefore flows through blood oxygenation element 70and to blood outlet manifold 47. In accordance with one aspect of thisinvention, the annular fiber bundle also provides some filtration ofblood passing through blood processing component 31, by filtering outparticulate matter that has passed through filter material 59 employedin gas removal/blood filter 56.

The lower portion of central void 51 communicates with pump space 55, inwhich centrifugal impeller 75 is disposed. Impeller 75 includes aplurality of vanes 76 and is mounted on shaft 77 via bearings 78.Impeller 75 preferably comprises an injection-molded part that enclosesa ferromagnetic disk, so that the disk may be magnetically coupled todrive unit 32 (see FIG. 1). Blood accelerated by impeller 75 is ejectedfrom pump space 55 via a passageway that includes curved ramp 79. Ramp79 serves to redirect radially outward blood flow from impeller to alongitudinal flow within blood inlet manifold 48.

In a preferred embodiment, oxygen is introduced into upper gas plenum 52through gas inlet port 44, passes through the interiors of themultiplicity of hollow fibers in blood oxygenation element 70. Carbondioxide, any residual oxygen, and any other gases exchanged throughblood oxygenation element 70 exit into lower gas plenum 54, and areexhausted through gas outlet port 45.

In accordance with the present invention, blood processing component 31also includes sensor 37 that monitors the level of gas or blood in gascollection plenum 50. Sensor 37 may sense a parameter indicative of alevel or volume of air or other gas in gas collection plenum 50, or maysimply detect the absence of blood, and may be any suitable sensor thatpreferably operates by a non-contact method. Suitable sensor methodsinclude electrical-charge based, optical and acoustic methods. Aresistive contact method also could be employed, in which a lowelectrical current is passed between adjacent electrodes only in thepresence of blood.

Sensor 37 preferably is of a capacitance type, per se known in the art,that detects a change in electrical capacitance between the bulk of aliquid (in this case, blood or saline) and gas. Alternatively, sensor 37may be optical in nature, and use a light source that has a wavelengththat is minimally attenuated by blood. In this case, the light source isdirected, at an oblique angle, through the blood at the top of the gascollection plenum towards a photodetector, and the sensor is positionedto detect the change in the refractive index of the blood (or salineprime) caused by the presence of air or other gases. In anotheralternative embodiment, sensor 37 may use an ultrasonic energy sourceand receiver to detect the presence of gas or absence of blood by thechange in acoustic transmission characteristics.

The output of sensor 37 is supplied to controller 33 of blood handlingsystem 30 (see FIG. 1) which in turn regulates valve 36. When sensor 37outputs a signal indicating that gas is present in gas collectionplenum, controller 33 opens valve 36, thereby coupling gas collectionplenum 50 to suction source 34, such as a vacuum bottle, pump orstandard operating room suction port, to evacuate the gas. Once the gasis evacuated, and the sensor detects blood at an appropriate level ingas collection plenum 50, the sensor changes its output.Correspondingly, controller 33 then closes valve 36. In this manner, gasis continuously monitored and then automatically removed from the bloodby blood handling system 30.

Referring now to FIG. 4, additional features of the present inventionare described. FIG. 4 is a cross-sectional view of apparatus similar tothat of FIG. 3, but in addition includes one or more relief areas 80that extend radially inward from blood oxygenation element 70. Reliefareas 80 preferably are disposed at a radially inward portion of theblood oxygenation element 70 opposite blood inlet manifold 48 and bloodoutlet manifold 47. Relief areas 80 permit the annular fiber bundle toexpand into the relief areas during operation, whereas the annular fiberbundle 70 occupies the position indicated by dotted lines 81 prior tooperation.

In addition, in accordance with the progressive filtration aspect of thepresent invention, filter material 85 may be disposed between theannular fiber bundle and the entrance to blood outlet manifold 47.Filter element 85 provides an additional third stage of filtration forblood passing through blood processing component 31, and preferablycomprises a screen-like material having the same or smaller effectivepore size than the filter material included in gas removal/blood filter56. Because blood has already passed through two stages of filtrationbefore reaching filter element 85 (i.e., gas removal/blood filter 56 andthe fibers of blood oxygenation element 70), it is expected that thisfilter will be capable of sustaining extended use without clogging.

In operation, deoxygenated blood from patient P is routed through one ormore lines 14-16 to blood inlet 41 of blood processing component 31.Blood entering gas collection plenum 50 is induced to circulate aroundthe exterior of gas removal/blood filter 56 until air or other gasesentrapped in the blood separate out of the blood and collect in theupper portion of the gas collection plenum. Responsive to the detectionof the presence of a predetermined level or volume of gas by sensor 37,controller 33 controls operation of valve 36 to evacuate the gas.

Applicant has observed in prototype designs that the gas removal systemof the present invention is capable of removing large amounts of airfrom the extracorporeal blood circuit during initial startup, therebygreatly reducing the amount of saline or donor blood required to primethe system. Advantageously, this feature facilitates rapid and easyset-up of the blood handling system, as well as reduces the amount ofsaline or donor blood delivered to the patient.

As blood circulates around gas removal/blood filter 56 in central void51, it is drawn by the negative pressure head created by impeller 75through filter material 59 and down through central void 51 into pumpspace 55. Rotation of impeller 75 caused by drive unit 32, under thecontrol of controller 33, propels blood up curved ramp 79 into bloodinlet manifold 48.

From blood inlet manifold 48, the blood traverses blood oxygenationelement 70 where it exchanges carbon dioxide and other gases for oxygen.Oxygenated blood then passes through filter element 85, if present (seeFIG. 4), and into blood outlet manifold 47. Oxygenated blood then isdirected back to the patient through arterial line 12, or optionally, aportion of the oxygenated blood may be recirculated through line 22.

While blood handling system 30 of the present invention thus is used insubstantially the same manner as previously known blood handlingequipment, it does provide a number of advantages over previously knownblood handing equipment. First, the system is simple to use, withintegrated blood processing component 31 embodying a number of bloodhandling features. Thus, for example, the clinician is not required toconnect together a pump, oxygenator, or blood filter, thereby savingtime, space and priming volume.

Blood processing component 31 advantageously may serve as a progressive,distributed, blood filter that provides staged filtration of the bloodflow. Specifically, gas removal/blood filter 56 serves as a first filterstage to filter out matter having a size of 40-250 microns, the fibersof blood oxygenation element 70 serve as a second filter stage to filterout particulate matter having a size of approximately 100 microns andlarger, and filter element 85, if present at the entrance to the bloodoutlet manifold 47, provides a third filter stage that filters outmaterial having a size of 40 microns or larger.

Another advantage of the system of the present invention is that the gasremoval system facilitates priming of the system with significantly lesssaline or donor blood. As is conventional, before initiating bypasssupport, the entire system must be primed with blood to purge all airout of the system. When priming the system of the present invention,however, the patient's own blood pressure may be used to fill venouslines 11, 14-16 and blood processing component 31. Advantageously, thegas removal system may be used to actively remove air and draw bloodinto the blood processing component.

In particular, when the gas removal system is turned on, sensor 37 willdetect gas in the gas collection plenum 50 and will then actively removethe gas as described hereinabove. In this manner, extracorporeal circuit10 can be primed by operation of the gas removal system. Once bloodprocessing component 31 has been thus primed, drive unit 32 may beactivated, so that impeller 75 also may be operated together with thegas removal system to purge air from the circuit. Blood may berecirculated through line 22 and valve 23 until all air has been purgedfrom the system.

Yet another advantage of the system of the present invention is thatadditional blood processing elements 21 may be added to the systemduring operation, with the gas removal system priming the newly addeddevice during operation. When such an element 21 is added to the systemduring operation, line 16 is temporarily clamped to isolate the locationfor new element 21. Blood processing element 21 then is connected,unprimed, in line 16. The clamps then are opened, so that any air in newelement 21 is removed automatically by the gas removal system. The gasremoval system of the present invention therefore may be used to removeair while delivering blood to the patient or when simply circulating theblood through line 22 until it is confirmed that all air from newelement 21 has been removed.

Referring now to FIG. 7, gas removal element 90 constructed for use in astand-alone gas removal system in accordance with the present inventionis described. Gas removal element 90 is intended for use with previouslyknown extracorporeal bypass systems to provide some of the advantagesdescribed hereinabove.

Gas removal element 90 includes transparent housing 91 having bloodinlet 92, blood outlet 93, gas removal port 94, and sensor 95. Housing91 encloses gas removal/blood filter 96, which in turn comprisesgenerally conical upper wall 97, support structure 98 and filtermaterial 99. Upper wall 97, support structure 98 and filter material 99may be constructed as described with respect to the embodiments of FIGS.5 or 6 set forth hereinabove. When used in conjunction with a suctionsource and suitable controller, gas removal element may be used toremove air or other gases entrained in the blood in the venous line, aswell as to facilitate priming.

Referring to FIG. 8, an alternative embodiment of the blood processingcomponent of the present invention is described. In FIG. 8, likecomponents of the embodiment of FIG. 3 are indicated by referencenumerals increased by 100. Thus, blood processing component 100comprises housing 140 having sensor 137, blood inlet 141, blood outlet142, recirculation outlet 143, gas inlet port 144, gas outlet port 145,gas removal port 146, blood outlet manifold 147, blood inlet manifold148, gas collection plenum 150, central void 151, upper gas plenum 152,annular fiber bundle compartment 153, lower gas plenum 154 and pumpspace 155. Gas removal/blood filter 156 is disposed in gas collectionplenum 150, blood oxygenation element 170 is disposed in annular fiberbundle compartment 153, and impeller 175 is rotatably fixed in pumpspace 155.

Blood processing component 100 differs from the embodiment of FIG. 3 inthat: (1) gas removal/blood filter 156 is positioned entirely in gascollection plenum 150 and does not extend into central void 151; (2)blood oxygenation element 170 is shorter and wider than bloodoxygenation element 70; and (3) heat exchanger 180 is disposed on bloodinlet manifold 148.

Heat exchanger 180 includes inlet port 181 and outlet port 182, andenables heated or cooled liquid, such as water, to contact the bloodinlet manifold and thereby heat or cool the blood flowing therethrough.Heat exchanger 180 also may have tubes, fins or the like to enhance heattransfer, and may be positioned at any other suitable location, such asadjacent to impeller 175. Alternatively, heat exchanger 180 may use anyother suitable heat exchange structure, such as a resistive heaterelement disposed within pump space 155.

In addition, in the embodiment of FIG. 8, gas removal/blood filter 156comprises a pleated structure, rather a screen-like filter material.Operation of blood processing component 100 is as described above withrespect to the embodiment of FIG. 3, except that in addition the bloodtemperature may be altered as desired for a particular application.

Referring now to FIGS. 9 and 10, further details of the centrifugal pumpemployed in the blood processing component of the present invention aredescribed. Centrifugal pump 200 includes impeller 201 having a pluralityof arcuate vanes 202 integrally formed with disk 203. Shaft 204 includeslower portion 205 that is press fit or adhesive bonded into the bottomof housing 40 (see FIG. 3.), and upper portion 206 that accepts seal207, bearings 208 and sleeve 209. Sleeve 209 is press fit or adhesivebonded to the interior of a bore in hub 210 of impeller 201. Seal 207prevents blood from entering bearings 207.

As shown in FIG. 10, impeller 201 preferably comprises an injectionmoldable plastic, such as polycarbonate, and is case in two sections. Afirst section includes lower portion 211 of disk 203 and hub 210, andincludes a recess that accepts a ferromagnetic washer 212. In accordancewith another aspect of the present invention, washer 212 includesthrough holes 213, which permit the injection process to be completed.Holes 213 also serve to define magnetic poles in the washer, that permitthe impeller to become magnetically coupled to permanent magnets, orelectromagnets, employed in drive unit 32.

During a second step of the injection molding process, first section 211is placed in a suitable mold, and the remainder of impeller 201(illustratively shown at 214) is formed by injecting material into themold through holes 213 in the first section and washer 212. When fullymolded, washer 212 is completely encased in the plastic, to preventundesirable blood-metal interaction.

FIGS. 11A and 11B depict an illustrative embodiment of the bloodhandling system of the present invention. In this embodiment, from whichall blood, gas and electrical lines have been omitted for clarity,microprocessor-driven controller 33 (see FIG. 1) and a back-up batteryare enclosed in wheeled base 220. Pole 221 is mounted in base 220, andincludes support arm 222 that supports blood processing component 31 ondrive unit 32. Support arm 222 also carries solenoid 223 that controlsvalve 36, which is in turn coupled to a suction source, such as thehospital wall suction port found in most operating rooms. Pole 221 alsocarries support arm 224, which carries display screen 225. Screen 225preferably is a touch-sensitive screen coupled to the controller, andserves as both an input device for the blood handling system and adisplay of system function.

FIGS. 12A and 12B provide representative samples of the informationdisplayed on the main windows of the blood handling system. As will ofcourse be understood by one of ordinary skill in the art ofcomputer-controlled equipment, the software used to program operation ofthe controller may include a number of set-up screens to adjustparticular system parameters. FIGS. 12A and 12B are therefore thewindows that will most commonly be displayed by the clinician during aprocedure.

The display of FIG. 12A, includes an indicator of battery status, aseries of timers for pump operation, duration of cross-clamping, and anauxiliary timer, arterial and venous temperatures and pressures, asmeasured, for example, at the blood inlet and blood outlet of the bloodprocessing component, the speed of the centrifugal pump and thecorresponding blood flow rate. Preferably, the controller is programmedwith a number of algorithms for determining an appropriate blood flowrate during the procedure, as determined based on body surface area(BSA). The window also may display the value of BSA determined by theselected algorithm based on the patient's dimensions, and the suggestedblood flow rate.

The display of FIG. 12B includes much of the same information providedin the window of FIG. 12A, but in addition may display temperatures andpressures graphically as well as numerically, so that the clinician canquickly identify trends in the data and take appropriate correctivemeasures. In addition, a lower portion of the windows displayed in FIGS.12A and 12B may present system status or help messages, and includetouch sensitive buttons that permit to access the other availablefunctions.

Although preferred illustrative embodiments of the present invention aredescribed above, it will be evident to one skilled in the art thatvarious changes and modifications may be made without departing from theinvention. It is intended in the appended claims to cover all suchchanges and modifications that fall within the true spirit and scope ofthe invention.

1. Apparatus for oxygenating and pumping blood comprising: a housing; agas removal system coupled to the housing; a blood oxygenation elementdisposed within the housing; and a pump coupled in fluid communicationwith the blood oxygenation element.
 2. The apparatus of claim 1 whereinthe gas removal system comprises: a sensor that detects the presence ofgas within the housing and outputs a signal; and a controller thatcontrols operation of the apparatus responsive to the signal.
 3. Theapparatus of claim 2 wherein the gas removal system further comprises: aline adapted to be coupled to a suction source; and a valve coupled tothe line between the housing and the suction source, wherein the valveis operated responsive to the controller.
 4. The apparatus of claim 1wherein the blood oxygenation element comprises an annular fiber bundle.5. The apparatus of claim 4 wherein the housing includes a central voidand the annular fiber bundle is disposed surrounding the central void.6. The apparatus of claim 5 wherein the gas removal system furthercomprises a filter element disposed at least partially in the centralvoid.
 7. The apparatus of claim 6 wherein the filter element furthercomprises at least one baffle.
 8. The apparatus of claim 5 wherein thegas removal system further comprises a filter element disposed at aninlet to the central void, the filter element comprising a pleatedmaterial.
 9. The apparatus of claim 1 wherein the housing includes ablood inlet manifold and a blood outlet manifold, and the blood inletmanifold is disposed on a diametrically opposite side of the housingfrom the blood outlet manifold.
 10. The apparatus of claim 9 wherein thepump is disposed within the housing.
 11. The apparatus of claim 1,further comprising a heat exchanger mounted to the housing. 12.Apparatus for oxygenating and pumping blood comprising: a housing; ablood oxygenation element having an annular fiber bundle disposed withinthe housing surrounding a central void, the blood oxygenation elementhaving an inlet and an outlet, the inlet being disposed on adiametrically opposite side of the annular fiber bundle from the outlet;and a pump coupled in fluid communication with the blood oxygenationelement, the pump having a pump inlet and a pump outlet coupled to theinlet.
 13. The apparatus of claim 12 wherein the housing includes aninlet manifold and an outlet manifold, the inlet manifold extendingalong a first side of the housing and the outlet manifold extendingalong a diametrically opposite side of the housing.
 14. The apparatus ofclaim 13 wherein the housing further includes a relief area on aninterior wall of the housing opposite to at least one of the inletmanifold and the outlet manifold.
 15. The apparatus of claim 12 whereinthe pump is mounted within the housing below the blood oxygenationelement.
 16. The apparatus of claim 12, further comprising a gas removalsystem.
 17. The apparatus of claim 16 wherein the gas removal systemcomprises: a sensor that detects the presence of gas within the housingand outputs a signal; and a controller that controls operation of theapparatus responsive to the signal.
 18. The apparatus of claim 17wherein the gas removal system further comprises: a line adapted to becoupled to a suction source; and a valve coupled to the line between thehousing and the suction source, wherein the valve is operated responsiveto the controller.
 19. The apparatus of claim 16 wherein the gas removalsystem further comprises a filter element disposed at least partially inthe central void.
 20. The apparatus of claim 16 wherein the filterelement further comprises at least one baffle.
 21. The apparatus ofclaim 16 wherein the gas removal system further comprises a filterelement disposed at an inlet to the central void, the filter elementcomprising a pleated material.
 22. A gas removal system for removing airfrom blood, comprising: a housing having an interior, a blood inlet anda blood outlet; a sensor positioned to sense gas within the interior ofthe housing; and a filter element disposed within the interior of thehousing.
 23. The gas removal system of claim 22 wherein the filterelement is substantially cylindrical
 24. The gas removal system of claim23 wherein the filter element comprises a pleated material.
 25. The gasremoval system of claim 22, wherein the sensor uses a sensing techniqueselected from the group consisting of: detection by capacitance, directresistance, light absorbance, light refractance, and ultrasonic energytransmittance.
 26. The gas removal system of claim 22, furthercomprising a valve operably coupled to the sensor, the valve openingresponsive to detection of gas by the sensor.
 27. The gas removal systemof claim 22, further comprising at least one baffle disposed within thefilter element.
 28. Apparatus for removing gas from a blood flow,comprising: a housing having an interior; an inlet leading to theinterior; an outlet coupled to the interior for removing blood from theinterior; a filter element disposed within the housing and positioned toseparate the inlet from outlet so that blood entering the inlet mustpass through the filter element; and a sensor coupled to the housing,the sensor determining whether gas is present.
 29. The apparatus ofclaim 28 wherein the inlet directs the blood in a substantiallytangential direction so that blood initially circulates within theinterior.
 30. The apparatus of claim 28 wherein the sensor is operablycoupled to a valve, the valve opening when the sensor determines thatgas is present.
 31. The apparatus of claim 28 wherein the valve isadapted to be coupled to a source of suction.
 32. A method of priming ablood handling system, comprising the steps of: providing a gas removalsystem, a blood oxygenation element and a pump, the gas removal devicehaving a sensor that detects whether the presence of gas, the sensoroperably coupled to a valve that opens when gas is detected by thesensor to permit removal of the gas; coupling the gas removal device,blood oxygenation element and pump to an arterial cannulae and a venouscannulae; and priming the system with blood or saline to remove air fromthe system by activating the gas removal system.
 33. The method of claim31 wherein the providing step is carried out with the gas removal devicebeing mounted to a common housing with at least one of the pump and theblood oxygenation element.
 34. The method of claim 33 wherein theproviding step is carried out with the gas removal device being mounteda housing that encloses the pump and the blood oxygenation element.